The present invention relates to a planetary gear set.
A known planetary gear set comprises a sun gear, a pinion carrier and a ring gear. The pinion carrier rotatably supports a plurality of pinions, each in mesh with the sun and ring gears. In order to support the pinions, a pinion shaft extends through each of the pinions and has one and opposite end portions fixedly supported by axially spaced plate portions of the carrier, and needle bearings are disposed between the pinion and the pinion shaft. There is a growing demand for miniaturization of planetary gear sets. To meet this growing demand, difficulty has been experienced in constructing gear sets which can withstand the thrust to which the needle bearings are subjected upon rotation of the associated pinion. This is because the use of an O-ring within a narrow space available for withstanding the thrust results in generation of heat. Thus, the use of O-ring is impractical.
An object of the present invention is to construct a planetary gear set which can withstand the thrust to which the needle bearings are subjected without any substantial generation of heat.